This invention relates to a device before securing a flexible element such as tubing or electrical cable in a manner which prevents strain resulting from an axial stress in the cable from being transmitted from one side of the device to another while permitting strain due to portional stress to be freely transmitted. The new stress/strain relief device is illustrated herein as being used to secure an electrical cable but the term "cable", which is used for the sake of brevity, should be understood to include various elongated flexible elements such as tubing, rope, and the like.
Cables that are secured with known types of stress/strain relief devices where they run into movable equipment or appliances, by movements of the operator. When a cable comprised of an insulating sleeve surrounding plurality of insulated conductors is gripped in a prior art-type of strain relief device and is twisted about it's longitudinal axis near the place where it is gripped, it and the conductors will form a short pitch longitudinally extending helix. This will result in high internal stress being developed in the cable. On the other hand, if a twist through the same rotational angle is applied at a greater distance from the place where the cable is gripped, the helix has a longer pitch and there is a corresponding reduction in internal strain. The term "stress" is used herein as having it's customary meaning which is to indicate the torsional or tensile force applied to a cable and the term "strain" is used to indicate the movement or stretch of the cable which may be caused by the stress or other forces applied to the cable.
Although many devices purporting to relieve or distribute torsional strain in a flexible element have been devised previously, none are perceived to provide for rotation of the flexible element freely about it's longitudinal axis while it is engaged in a strain relief device. The known strain relief devices fix a portion of the flexible element to a stationery support through which the flexible element passes. Consequently, none of the known devices provide for transmitting or relieving stress resulting from torsional or other applied forces.